In recent years the pharmaceutical industry has developed an effective panoply of therapeutic compounds for the treatment of human disease. Antibacterial compounds such as penicillin, the sulfa drugs, and more recently, aminoglycocide and cephalosporin antibiotics have drastically reduced fatalities from bacterial infection. Viral infections, once thought to be untreatable, can now be controlled with antiviral agents, notably nucleoside analogs such as acyclovir and related compounds. A diagnosis of cancer, at one time a virtual death sentence, is now simply a prelude to often-successful treatment with antineoplastic drugs such as methotrexate. Even epilepsy, whose victims were thought to have been chosen by the gods as special vehicles of divine possession, has yielded to the protection of dopamine. AIDS itself, the newest and most frightening of our diseases, has been at least retarded in its progress by nucleoside replication inhibitors such as AZT (3'-azido-3'-deoxythymidine).
Effective as these pharmaceuticals are, however, once inside the patient's body, many are quickly inactivated by degrading enzymes, particularly deaminases. In some cases, for example when it is necessary for the active drug to cross the blood-brain barrier, undesirably large doses of the drug must be administered in order to ensure enough will remain in circulation long enough to reach the brain in therapeutic quantities. In other cases, drugs must be administered continuously, effectively tying the patient to the iv needle, in order to provide enough active form of the drug in circulation without having to administer toxically high concentrations.
It is thus desirable to provide therapeutic compounds in a form which will persist for a longer time in the patient's body without degrading than drugs currently in use.
A number of efforts have been made to improve these effective pharmaceuticals by increasing their lipophilicity by attaching lipophilic groups such as acetyl or even cholesterol so as to allow faster penetration into intercellular spaces and compartments with lipophilic barriers, such as the blood-brain barrier. However, these measures have not always been as effective as desired.
One class of particularly effective antiviral pharmaceuticals which has been used in the treatment of herpes viruses as well as other viruses, particularly in immunocompromised patients such as those infected with the AIDS virus, are nucleoside analogs. These analogs, after phosphorylation by the enzymes of the cell, disrupt DNA synthesis and are thus useful as anticancer agents as well as inhibitors of virus multiplication. One of the early compounds used for this purpose was 5-iodo-2'-deoxyuridine (IDU). [Darby, G. (1995), "In search of the perfect antiviral," Antiviral Chem. & Chemother. 1:54-63]. This article discloses that such drugs also tend to be toxic to normal cells due to the fact that they inhibit DNA replication. Acyclovir and valaclovir are mentioned as particularly useful compounds in this regard because they become phosphorylated only within infected cells, and thus inhibit DNA replication only in these cells. These drugs, however, have low oral bioavailability (15-20%), which limits their usefulness. Again, a method for increasing the half-lives of such drugs is needed.
Vidarabine, 9-(.beta.-D-arabinofuranosyl)adenine (ara-A) was originally discovered as an antitumor agent [Reist, E. J. et al., "Potential anticancer agents. LXXVI. Synthesis of purine nucleosides of .beta.-D-arabinofuranose," J. Org. Chem. (1962) 27:3274-3279] and in later studies, it was shown to be active against herpes simplex virus type 1 and 2 [Drach, J. C. and Shipman, C. Jr., "The selective inhibition of viral DNA synthesis by chemotherapeutic agents: an indicator of clinical usefulness?" Ann. NY Acad Sci (1977) 284:396-409; Andrei, G. et al., "Comparative activity of various compounds against clinical strains of herpes simplex virus," Eur. J. Clin. Microbiol. Infect. Diseases (1992) 11:143-151]. Ara-A is a licensed compound for the treatment of herpes simplex keratitis [Denis, J. et al., "Treatment of superficial herpes simplex hepatitis with Vidarabine (Vira A): A multicenter study of 100 cases," J. Fr. Ophthalmol. (1990) 13:143-150] and encephalitis [Whitley, R. J., "Herpes simplex virus infections of the central nervous system. Encephalitis and neonatal herpes," Drugs (1991) 42:406-427; Stula, D. and Lyrer, P., "Severe herpes simplex encephalitis: Course 15 years following decompressive craniotomy," Schweiz. Med. Wochenschr. (1992) 122:1137-1140; Whitley, R. J., "Neonatal herpes simplex virus infections," J. Med. Virol. (1993), Suppl. 1, 13-21]. It has also been considered for the treatment of genital and disseminated herpes infections [DRUGDEX (R) Information System, Gelman, C. R. and Rumack, B. H., Eds.; MicroMedex, Inc., Englewood, Colo. 84, Expired May 31, 1995], cytomegalovirus encephalitis [Suzuki, Y. et al., "Cytomegalovirus encephalitis in immunologically normal adults," Rinsho. Shinkeigaku (1990) 30:168-173], chronic hepatitis B virus (HBV) infection [Chien, R. N. and Liaw, Y. F., "Drug therapy in patients with chronic type B hepatitis," J. Formos. Med. Assoc. (1995) 94(suppl. 1):s1-s9; Fu, X. X., "Therapeutic effect of combined treatment with ara-A, dauricine and Chinese herbs in chronic hepatitis B infection," Chung. Hua. Nei. Ko. Tas. Chih. (1991) 30:498-501] and acute non-lymphoid leukemia [Resegotti, L., "Treatment of acute non-lymphoid leukemia (ANLL) in elderly patients. The GIMEMA experience," Leukemia (1992) 6(suppl. 2):72-75]. Ara-A may also be an alternative therapy for acyclovir-resistant herpes simplex virus, cytomegalovirus and varicella-zoster virus infections [Chatis, P. A. and Crumpacker, C. S., "Resistance of herpes viruses to antiviral drugs," Antimicrob. Agents Chemother. (1992) 36:1589-1595; Nitta, K. et al., "Sensitivities to other antiviral drugs and thymidine kinase activity of acyclovir-resistant herpes simplex virus type 1," Nippon. Ganka. Gakkai. Zasshi (1994) 98:513-519]. However, the use of ara-A as a clinically effective agent is limited due to its rapid deamination to ara-H by adenosine deaminase (ADA) in vivo [Cass, E. C., "9-.beta.-D-Arabinofuranosyladenine (Ara-A)," In Antibiotics. Mechanism of Action of Anti-eukarvotic and Antiviral Compounds; Hahn, F. E., Ed.; Springer-Verlag: New York (1979) V:87-109; Whitley, R. et al., "Vidarabine: a preliminary review of its pharmacological properties and therapeutic use," Drugs (1980) 20:267-282] as well as its poor solubility in water.
There were several attempts to prevent the rapid metabolism of ara-A [Plunkett, W. and Cohen, S. S., "Two approaches that increase the activity of analogs of adenine nucleosides in animal cells," Cancer Res. (1975) 35:1547-1554], including the co-administration of adenosine deaminase inhibitors such as deoxycoformycin [Cass, C. E. and Ah-Yeung, T. H., "Enhancement of 9-.beta.-D-arabinofuranosyladenine cytotoxicity to mice leukemia L1210 in vitro by 2'-deoxycoformycin," Cancer Res. (1976) 36:1486-1491; LePage, G. A. et al., "Enhancement of antitumor activity of arabinofuranosyl adenine by 2'-deoxycoformycin," Cancer Res. (1975) 36(4):1481-1485; Cass, C. E. et al., "Antiproliferative effects of 9-.beta.-D arabinofuranosyladenine-5'-monophosphate and related compounds in combination with adenosine deaminase inhibitors against a mouse leukemia L1210/C2 cells in culture," Cancer Res. (1979) 39(5):1563-1569; Plunkett, W. et al., "Modulation of 9-.beta.-D-arabinofuranosyladenine-5'-triphosphate and deoxyadenosine-triphosphate in leukemic cells by 2'-deoxycoformycin during therapy with 9-.beta.-D-arabinfuranosyladenine," Cancer Res. (1982) 42(5):2092-2096; Agarwal, R. P. et al., "Clinical pharmacology of 9-.beta.-D-arabinofuranosyladenine in combination with 2'-deoxycoformycin," Cancer Res. (1982) 42(9):3884-3886] and A6-benzoyladenosine [Tritach, G. L. et al., "Synergism between the antiproliferative activities of arabinofaranosyladenine and N.sup.6 -benzoyladenosine," Cancer Biochem. Biophys. (1977) 2(2):87-90]. The effects of ara-AMP and ara-A in combination with erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) were 25 studied in mouse leukemia L1210/C2 cell culture and the results were promising [Cass, C. E. et al., "Antiproliferative effects of 9-.beta.-D arabinofuranosyladenine-5'-monophosphate and related compounds in combination with adenosine deaminase inhibitors against a mouse leukemia L1210/C2 cells in culture," Cancer Res. (1979) 39(5):1563-1569]. However, in the clinical trials with the combination of ara-A and deoxycoformycin some patients developed toxicities [Miser, J. S. et al., "Lack of significant activity of 2'-deoxycoformycin alone or in combination with adenine arabinoside in relapsed childhood acute lymphoblastic leukemia. A randomized phase II trial from children's cancer study group," Am. J. Clin. Oncol. (1992) 15:490-493]. Other approaches comprise the conjugation of ara-AMP to lactosaminated human serum albumin [Jansen, R. W. et al., "Coupling of antiviral drug ara-AMP to lactosaminated albumin leads to specific uptake in rat and human hepatocytes," Hepatology (1993) 18:146-152] and administration of ara-A in nanocapsules to improve the pharmacokinetic profiles [Yang, T. Y. et al., "Studies on pharmacokinetics of 9-.beta.-D-arabinosyladenine nanocapsules," Yao. Hsueh. Hsuech. Pao. (1992) 27:923-927]. 9-(.beta.-D-Arabinofuranosyl)-6-dimethylaminopurine (ara-DMAP), after its intravenous administration in rats and monkeys, was rapidly converted to 9-(.beta.-D-arabinofuranosyl)-6-methylaminopurine (ara-MAP) and other purine metabolic end products [Koudriakova, T. et al., "In vitro and in vivo evaluation of 6-azido-2'-3'dideoxy-2'-fluoro-.beta.-D-arabinofuranosylpurine (FAAddP) and 6-methyl-2',3'-dideoxy-2'-fluoro-.beta.-D-arabinofuranosyladenine (FMAddA) as prodrugs of the anti-HIV nucleosides, 2'-F-ara-ddA and 2'-F-ara-ddI," J. Med. Chem. In Press]. However, less than 4% of the dose of ara-DMAP was found to be converted to ara-A and the half-life of ara-A was four times longer.
Recently, in a metabolic study of AZT, Sommadossi et al. [Cretton, E. M. and Sommadossi, J- P, "Reduction of 3'-azido-2',3'-dideoxynucleosides to their 3'-amino metabolite is mediated by cytochrome P-450 and NADPH-cytochrome P-450 reductase in rat liver microsomes," Drug Metab. Dispos. (1993) 21:946-950; Wetze, R. and Eclstome, E., "Synthesis and reactions of 6-methylsulfonyl-9-.beta.-D-ribofuranosylpurine," J. Org. Chem. (1975) 40(5):658-660] have shown that the azide moiety in AZT is reduced to an amino moiety by the cytochrome-P 450 reductase system.
Didanosine (ddI) is a synthetic nucleoside analogue structurally related to inosine with proven activity against human immunodeficiency virus (HIV) [Faulds, D. and Brogden, R. N., "Didanosine: a review of its antiviral activity, pharmacokinetics properties and therapeutic potential in human immunodeficiency virus infection, " Drugs (1992) 44:94-116]. It is approved for use in patients who are intolerant to zidovudine (AZT) or who have deteriorated on zidovudine therapy. However, its various side effects [Tartaglione, T. A. et al., "Principles and management of the acquired inmmunodeficiency syndrome. In: Pharmacotherapy. A pathophysiologic approach, J. T. DiPiro et al. (Eds.) Appleton and Lange, Norwalk, Conn. (1993) 1837-1867), chemical instability in gastric acid and low oral bioavailability of 27-36% (Drusano, G. L. et al., "Impact of bioavailability on determination of the maximal tolerated dose of 2',3'-dideoxyinosine in phase I trials, " Antimicrob. Agents Chemotherapy (1992) 36:1280-1283] limit its usefulness. Furthermore, there is evidence that ddI enters the central nervous system and the cerebrospinal fluid (CSF) less readily than does AZT. The extent of ddI uptake in brain tissue and CSF, relative to that in plasma, was only 4.7 and 1.5%, respectively [Collins, J. M. et al., "Pyrimidine dideoxyribonucleosides: selectivity of penetration into cerebrospinal fluid," J. Pharmacol. Exp. ther. (1988) 245:466-470; Anderson, B. D. et al., "Uptake kinetics of 2'3'-dideoxyinosine into brain and cerebrospinal fluid of rats: intravenous infusion studies," J. Pharmacol. Exp. Ther. (1990) 253:113-118; Tuntland, T. et al., "Afflux of Zidovudine and 2'3'-dideoxyinosine out of the cerebrospinal fluid when administered alone and in combination to Macaca nemestina," Pharm. Res. (1994) 11:312-317].
In an effort to overcome the instability of ddI and 2'3'-dideoxyadenosine (ddA) in acidic conditions, the 2'-fluoro-.beta.-D-arabinofuranosyl derivatives 2'-F-ara-ddI and 2'-F-ara-ddA of the nucleosides have been synthesized [Marquez, V. E. et al., "Acid-stable 2'-fluoro purine dideoxynucleosides as active agents against HIV," J. Med. Chem. (1990) 33:978-985]. These authors reported that 2'-F-ara-ddA and 2'-F-ara-ddI were stable in acidic media and were as potent as the parent compounds in protecting CD4+ATH8 cells from cytopathogenic effects of HIV-1. However, 2'-F-ara-ddI, as well as ddI, are relatively hydrophilic and do not readily penetrate the blood-brain barrier (BBB) in mice [Shanmuganathan, K. et al., "Enhanced brain delivery of an anti-HIV nucleoside 2'-F-ara-ddI by xanthine oxidase mediated biotransformation," J. Med. Chem. (1994) 37:821-827]. Recently, applicants synthesized a more lipophilic prodrug, 2',3'-dideoxy-2-fluoro-.beta.-D-arabinofuranosyl-purine (2'-F-ara-ddP), which was converted to the parent nucleoside, 2'-F-ara-ddI by xanthine oxidase in vivo. Pharmacokinetic studies indicated 2'-F-ara-ddP increased the delivery of 2'-F-ara-ddI to the brain in mice. The AUC.sub.brain /AUC.sub.serum ratio for 2'-F-ara-ddI was increased to approximately 36% after oral and intravenous prodrug administration [Shamnuganathan, K. et al., "Enhanced brain delivery of an anti-HIV nucleoside 2'-F-ara-ddI by xanthine oxidase mediated biotransformation," J. Med. Chem. (1994) 37:821-827].
Cordycepin is potentially very active against tumor growth and viral replication [Yeners, K. et al., "Cordycepin selectively kills TdT-positive cells," Abstract of presentation to American Soc. of Clin. Oncology Meeting, May 1993]. However, the effectiveness of cordycepin in vivo is markedly decreased by rapid deamination. Cordycepin exhibits its biological activity through direct inhibition of viral replication through its ability to block polyadenylic acid [poly(A)] synthesis, thus interfering with processing and maturation of both cellular and viral MRNA. [Svendsen, K. R. et al. (1992), "Toxicity and metabolism of 3'-deoxyadenosine N'-oxide in mice and Ehrlich ascites tumor cells," Cancer Chemother. Pharmacol. (1992) 30:86-94.] Cordycepin is phosphorylated by adenosine kinase to 3'-deoxyadenosine monophosphate, with further phosphorylation by adenylate kinase to 3'-deoxyadenosine triphosphate which exerts toxic effects due to its incorporation into RNA in lieu of ATP, thereby functioning as a chain terminator.
In vivo, however, the effectiveness of cordycepin as an antitumor agent is limited gi because of very rapid deamination of the compound to yield 3'-deoxyinosine which is biologically inert. That reaction is catalyzed by adenosine deaminase. [Frederiksen, S. and Klenow, H. (1975), "3-Deoxyadenosine and other polynucleotide chain terminators," In Handbook of experimental pharmacology, (A. C. Sartorelli and G. Johnes, Eds.) 657-669.]
The in vivo antitumor activity of cordycepin can be enhanced by administration with adenosine deaminase inhibitor 2'-deoxycoformycin (2'-DCF). Administered together, cordycepin and 2'-DCF resulted in marked inhibition of L1210 and P388 cell growth in vitro and in mice models in vivo. [Johns, D. G. and Adamson, R. H. (1976), "Enhancement of the biological activity of cordycepin (3'-deoxyadenosine) by the adenosine deaminase inhibitor 2'-deoxycoformycin," Biochem. Pharmacol. (1976) 25:1441-1444.]
Another way to avoid deamination of cordycepin is through the use of 3'-deoxyadenosine N'-oxide (3'-dANO) as a prodrug. 3'-dANO is metabolically inert until it has entered a target cell that is capable of reducing 3'-dANO to cordycepin. [Svendsen, K. R. et al. (1992), "Toxicity and metabolism of 3'-deoxyadenosine N.sup.1 -oxide in mice and Ehrlich ascites tumor cells," Cancer Chemother. Pharmacol. (1992) 30:86-94.]
Reduction to the amine has been observed to adversely affect the bioavailability of other drugs as well. Reduction to the amine has been shown to deactivate the antitumor agent meta-azidepyrimethamine. [Kamali, F., et al. (1988), "Medicinal azides. Part 3. The metabolism of the investigational antitumor agent meta-azidepyrimethamine in mouse tissue in vitro," Xenobiotica 18:1157-1164.]
This invention provides azide compounds, preferably azide derivatives of therapeutically active substances which provide increased half-lives for the therapeutically active substances.
Azide derivatives of certain biologically active compounds have been synthesized for the purpose of optical imaging. [Nicholls, D., et al. (1991), "Medicinal azides. Part 8. The in vitro metabolism of p-substituted phenyl azides," Xenobiotica 21:935-943.]
Azide drugs such as 3'-azido-3'-deoxythymidine (AZT, also known as zidovudine) have been used in the treatment of AIDS because of their inhibition of viral replication. [Tartaglione, T. A., et al. (1993), "Principles and management of the acquired immunodeficiency syndrome. In: Pharmacotherapy. A pathophysiologic approach, DiPiro, J. T. et al., eds., Appleton and Lange, Norwalk, Colo. 1837-1867.] AZT is reduced in vivo to the corresponding amino compound. [Placidi, L., et al. (1993, "Reduction of 3'-azido-3'-deoxythymidine to 3'-amino-3'-deoxythymidine in human liver microsomes and its relationship to cytochrome P450," Clin. Pharmacol. Ther. 54:168-176. This is also true of azidodideoxynucleosides. Cretton, E. M. and Sommadossi, J- P (1993), "Reduction of 2'-azido-2',3'-dideoxynucleosides to their 3'amino metabolite is mediated by cytochrome P-450 and NADPH-cytochrome P450 reductase in rat liver microsomes," Drug Metab. Dispos. 21:946-950.] The degradation product of AZT is not therapeutically effective and is, in fact, toxic. [Cretton, E. M. et al., "Catabolism of 3'-azide-3'-deoxythymidine in hepatocytes and liver microsomes with evidence of formation of 3'-amino-3'-deoxythimidine, a highly toxic catabolite for human bone marrow cells," Molec. Pharmacol. (1991) 39:258-266.]
Kumar, R., et al. (1994), "Synthesis, in vitro biological stability, and anti-HIV activity of 5-halo-6-alkoxy (or azide) -5,6-dihydro-3'-azido-3'deoxythymidine (AZT)," J. Med. Chem. 37:4297-4306, reported that 6-azide derivatives of AZT were 2-3 log units less active than AZT.
An azide derivative of 2,6-diaminopurine as well as several other derivatives of 2,6-diaminopurine have also been recognized as potent inhibitors of HIV replication. These compounds also inhibit adenosine deaminase and inhibit the deamination of 9-beta-D-arabinofuranosyladenine (araA). [Balzarini, J. and DeClercq, E. (1989), "The antiviral activity of 9-beta-D-arabinofuranosyladenine is enhanced by the 2',3'-dideoxyriboside, the 2',3'-didehydro-2',3'-dideoxyriboside and the 3'-azido-2',3'-dideoxyriboside of 2,6-diaminopurine," Biochem. Biophys. Res. Commun. 159:61-67.]
A method as provided herein, is needed for increasing the half-life of pharmaceutically active compounds so as to avoid problems associated with the rapid degradation of the compounds in the patient's body.